There are three different forms of vein pattern recognition: palm vein pattern recognition, finger vein pattern recognition (both of which work using near-infrared* light) and retina vein pattern recognition.
*‘Near’-infrared light is infrared light with a short wavelength.
1. Palm vein pattern recognition
The haemoglobin in your blood contains oxygen when it is transported from your lungs to the tissues in your body by your arteries. By the time the blood flows back to your heart via different arteries this oxygen has been released. Vein pattern recognition uses this difference between deoxidised and oxygenated haemoglobin. Deoxidised haemoglobin absorbs infrared light, making the vein pattern visible if you use a scanner to illuminate it with infrared light.
Everyone has a unique vein pattern in their palm. Reference points in the pattern can therefore be stored and the pattern can be used as an identification and security technique. Most systems that use vein pattern recognition store the vein pattern as an image, which may or may not be encoded. With the Palm-ID, on the other hand, the scanned reference points are stored directly as an encrypted template, which means the vein pattern is converted into code inside the scanner itself. This method of palm vein pattern recognition therefore offers an extremely high level of security.
2. Finger vein pattern recognition
Finger vein pattern recognition is based on the same principle as palm vein pattern recognition. Illuminating the vein pattern in the fingers using near-infrared light makes it possible to discern this pattern, thanks to the deoxidised haemoglobin.
In the case of a finger scan the surface area you are dealing with is much smaller, however. That means, on the one hand, that this is a more compact technique than palm vein pattern recognition, as the scanner is simply a smaller device. On the other hand, it is less user-friendly, as the finger has to be positioned more precisely on the scanner. The smaller surface area means that there are fewer reference points, making it more difficult to recognise the pattern correctly. When it comes to vein pattern recognition, the more reference points there are, the greater the level of security and convenience that will be achieved.
3. Retina vein pattern recognition
The human retina is a thin layer of tissue at the back of the eye. Because of the complex structure of capillaries that supply blood to the retina, every retina is unique.
Retina vein pattern recognition involves scanning the retina by shining (non-infrared) light through the eyeball. As the blood vessels in the retina absorb this light, the vein pattern can be discerned and stored as an image. Retina vein pattern recognition is becoming less popular, mainly because it is not a user-friendly technique. To ensure it works correctly, users have to keep their head completely still. They also have to stand at just the right height and just the right distance from the scanner. Many people also do not like the idea of having light shone in their eyes.